Deore cranks with the trekking rings (26/36/48) taken off. 26 and 36 moved to my geared FS as a 2×9, 48t sold on for a tenner. Adds up to new rings for the FS bike and a new set of cranks and BB for the singlespeed for about 40 notes. Tiny weight increase over the XTs on my full suss bike, too. At the moment, I can’t imagine replacing those old XTs with anything other than a pair of Deores. I’d rather spend the money on something more important, like new forks.
I’ve run truvativs in the past, and didn’t get on with the fastening system. Square taper is great – in 20 odd years, I’ve neer had a problem I didn’t cause myself. I have to say that after trying a bunch of other options, Shimano still kicks bottom in terms of reliability and price.